This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The early diagnosis of a neurological disease often aids in the treatment of disease symptoms. Among other things, iron accumulation has been associated with several neurological diseases (Sehgal et al. 2005). Differences in magnetic susceptibility images are particularly sensitive to tissues containing iron. In nuclear MR, susceptibility imaging exploits these susceptibility differences to extract phase information from a gradient echo sequence scan and generate images that achieve a form of contrast not found in standard magnitude images. In 2005, it was suggested by Sehgal et al that susceptibility imaging will be faster and yield better SNR at higher field strengths. Characterizing magnetic susceptibility differences at different field strengths would allow the improvements from increasing the field strength used for susceptibility imaging to be quantified.
The specific aims of this project are to examine and characterize: 1) the effect of perfusion fixations on susceptibility images, noting differences in scans performed in vivo and ex vivo following perfusion. 2) any field strength dependence exhibited in the susceptibility images. 3) T2* decay by taking a series of scans varying TE, paying particular attention to non-exponential decay and its relationship to phase using combined magnitude and phase images. I will gather phase and susceptibility images of the mouse brain using a gradient echo sequence (GPSW). The mice brains will be scanned under each of the following 3 conditions: 1) In vivo at 7T, with TE H12 ms, TR H 100 ms, alpha H 20 degrees, averaging enough excitations offline to arrive at a SNR similar to condition 2 at 9T. 2) Perfusion with saline at 1T, 2T, 7T, and 9T. 3) Perfusion with gadolinium (ProHance) at 1T, 2T, 7T, and 9T, TE H7ms, TR H100 ms, alpha H90 degrees, NEX = 2 Scan resolution for the 7T and 9T scans will be 256 x 128 x 128 for a 22mm x 11mm x 11mm, 3D isotropic rectangle image. For 1T and 2T, resolution will be 128 x 64 x 64. After the in vivo scans, it is desired, but not necessary, to perform perfusion on the brains of the mice that survive for use in conditions (2) and (3) above. If those animals are not suitable for perfusion for some reason, then additional mice will be required for the perfusion studies.